Creating Pages For Specific Type of Posts

What I’m doing:

Building a blog for my friend’s start-up: https://glamourmill.com
I’m currently using the default theme/temlate. I’ve created different pages based on the type/categories of posts she will create. I’ve also posted a test Youtube embed.

Problem:

Currently if I tag a post, and then click on a link of that tag, wp takes me to an excerpt page which has very short summaries of those posts and do not display the actual embedded video.

Goal:

She will be adding many types of posts, —just text, photos & videos and so forth. What I want to happen is that when one of her readers clicks on the link tag (ex. say ‘video’) or category (ex. ‘video), I want them to be taken to a page that shows all posts that are tagged or categorized with (ex. video) in their full length (or at least show the embedded images and videos and cut off some text.

Attempts:

I have seen a few posts that suggest I search and replace all instances of the-excerpt and replace it with the-content:
https://codex.www.ads-software.com/Function_Reference/the_excerpt
But I have searched for that function within my current default (theme: Twenty Ten 1.1 by the WordPress team) archive and category php’s, but come up short. Modifying them nevertheless has created endless loops that made my Firefox not like me very much.

Parting Notes:

I’m a complete beginner so bare with me if this problem is nothing less than an itch.

Thanks in advance.